Patent Document 1 discloses a side airbag to be installed in a side portion of a seatback of a vehicle seat close to outside of a vehicle.
Internal of the side airbag are formed a first flow path and a second flow path. The first flow path causes a gas ejected from gas ejection ports of an inflator to flow toward the upper portion of an airbag that protects the side of the occupant's head. The second flow path causes the gas to flow from the upper portion of the airbag toward the lower portion of the airbag that protects the side of the occupant's chest. The airbag is configured to in, for example, a vehicle side-impact collision, cause a gas to flow from the inflator into the first flow path to inflate and deploy the upper portion of the airbag toward the side of the head, and simultaneously, cause the gas to flow from the upper portion of the airbag into the second flow path to inflate and deploy the lower portion of the airbag toward the side of the chest.
At the intermediate position of the side airbag in its front-rear direction is formed a seam portion obtained by overlapping and sewing left and right base fabrics. The first flow path is formed between the seam portion and the upper half portion of the rear edge of the side airbag. The second flow path is formed between the upper edge of the seam portion and the front edge of the side airbag.